A. Field of the Invention
The present invention relates to a method for electromagnetic dynamic plasticating extrusion to be used in the sphere of processing polymer materials, and the equipment designed for realizing the method.
B. Description of Related Art
Prior to the present invention, the chief equipment used in the processing of polymers was various types of screw extruder. The screw extruder is required to work in a required steady state and the solid material is conveyed entirely by friction. Compaction of material proceeds slowly while the pressure that is established is fairly low and venting of gases inefficient, resulting in low conveying efficiency. Plasticating and melting relies chiefly on exterior heating and heat caused by shearing. The melting rate is low and plastication uneven. Mixing which depends entirely on the process of shearing is not very efficient. Melt pumping depends mainly on the shearing of the melt, and since the material being processed has a high viscosity and elasticity, resistance to melt pumping is fairly high, leading to low pumping rates. Due to the above-mentioned drawbacks in extrusion methods there are limits to increasing output and improving the quality of the extrusion. Due to the high temperatures of extrusion, increase in output is also limited by the slow cooling rate of the attached auxiliary equipment. Besides, it is also difficult to overcome the random disturbances caused by different variables, thus limiting improvement in the quality of extrusion products.
The conventional screw extruder consists of the following systems: power transmission, extruding, heating and cooling and control. The extruding system comprises the screw, which is also the heart of the screw extruder. For a long time, attention has generally been focussed on research in the screw's structure and its mechanisms; therefore its structure has been improved continuously, with the result that there are now many different new types of screw extruder. But, the new screw extruders, whatever their improvements, all have to be fitted with an independent drive motor and power transmission, thus increasing the size of the screw extruder. It also leads to such drawbacks as energy loss during power transmission, leakage of lubricants and pollution, friction and wear of machine parts and noise caused by contact of machine parts and finally poor stress bearing condition. Again, because the screw has a large length to diameter L/D ratio (normally greater than 20) and with increasing requirments on increasing output and improving product quality, the usual method of solving the contradiction between output and quality, using conventional technology, is to increase the L/D ratio of the screw. But increase in L/D ratio is always accompanied by a corresponding increase in the difficulty of screw and barrel manufacture, increased cost of machining and an overall increase in size and weight of the machine. At the same time, the friction and wear between screw and barrel is worsened, which not only directly affects the life of the extruder but also greatly increases energy consumption.